Aluminium wrought alloy

ABSTRACT

The invention relates to an aluminium wrought alloy with an aluminium matrix, in which at least a soft phase and hard particles are incorporated, the soft phase being at least one element from a first group of elements consisting of tin, antimony, indium and bismuth and the hard particles being scandium and/or zirconium and at least one element from a second group of elements consisting of copper, manganese, cobalt, chromium, zinc, magnesium, silicon and iron, or inter-metallic phases of scandium, zirconium with aluminium or aluminium with the elements from the second group of elements. The first element(s) from the first group of elements is (are) present in a quantity of a total of 4.5% by weight maximum, the element(s) from the second group of elements is (are) present in a quantity of a total of 8.5% by weight maximum and the scandium and/or zirconium is (are) present in a quantity of a total of 0.8% by weight maximum.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to an aluminium wrought alloy with analuminium matrix in which a soft phase and hard particles areincorporated, the soft phase being an element from a first group ofelements consisting of tin, antimony, indium and bismuth and the hardparticles being scandium and/or zirconium and at least one element froma second group of elements consisting of copper, manganese, cobalt,chromium, zinc, magnesium, silicon and iron, as well as scandium and/orzirconium or inter-metallic phases of scandium, zirconium with aluminiumor aluminium with the elements from the second group, a base layer for abearing element made therefrom, which can be disposed between aprotective shell and a running layer of the bearing element, as well asa bearing element with a protective shell, a running layer and a baselayer disposed in between.

[0003] 2. The Prior Art

[0004] Alongside many other development trends in the engine-buildingindustry today, there are two main aspects which can be singled out.First of all, engines are becoming increasingly more powerful and,secondly, these engines are becoming increasingly lightweight. Theso-called “three-litre car”, which is promoted in the various media atregular intervals, is an example of this trend. These specificationspursued by the automotive industry have had a knock-on effect on thevarious industries supplying accessories, such as the manufacturers ofbearing elements, for example. As a result, bearings, such as plainbearings for example, have developed accordingly in recent years. Thestarting point was originally the single-layer bearing, from which thecurrent multi-layer bearing was developed in order to meet the variousrequirements placed on such bearings, such as capacity to withstandload, lubricating capacity, etc.. This type of bearing generallyconsists of a protective shell (usually made of steel) designed toabsorb mechanical stress, on top of which a layer of the respectivebearing alloy is applied. Another thin coating, also known as an“overlay”, is usually disposed on top of the bearing alloy, which may begalvanically produced, for example. This other, very thin layer normallycontains a very high proportion of so-called soft phases, such as leador tin for example, which impart to this layer an ability to adapt toand embed abraded material from the parts to be mounted, such as shafts.Due to the fine thickness of this “overlay”, this layer is alsomechanically capable of withstanding a sufficient degree of stress andserves as the so-called running layer. The bearing metal layerunderneath ensures that the bearing also remains serviceable even if therunning layer is extensively worn, for which purpose this bearing metallayer also contains an appropriate proportion of so-called soft phases.In order to prevent soft phases from migrating from the running layerinto the bearing metal layer, thereby preventing a degree of brittlenessthat would otherwise occur, a barrier may be provided between therunning and bearing metal to prevent migration, for example of tin. Thisdiffusion barrier may be made from nickel.

[0005] It is also standard practice to apply a so-called binding filmbetween the protective shell and the bearing metal, in order tocompensate for the properties specific to the materials of the twolayers with a view to obtaining sufficient cohesion of the bearing, evenwhen subjected to extensive stress. This binding film may be made fromaluminium, for example.

[0006] A bearing of this type is known from patent specification WO98/17833 A. This WO-A patent describes in particular an aluminium alloyfor a layer, specifically for a plain bearing, which is free of siliconexcept for the impurities resulting from the melting process, and, inaddition to tin, contains as the main alloying element, at least oneelement each from the group of elements consisting of lead and bismuthon the one hand and from the group consisting of magnesium and zinc onthe other. The minimum proportion of tin is 16% by weight. All the otherelements in the alloy are limited to a total of at most 11% by weight.The proportion of the respective element from the group which alsocontains antimony and indium in addition to lead and bismuth is between10% and 75% of the maximum solubility of the respective element byreference to the total tin content.

[0007] From the background art, it has been suggested—e.g. in patentspecification WO 97/22725 A—that in order to improve the tribologicalproperties, aluminium alloys for plain bearings which contain tin as themain alloying element should contain an added hard substance selectedfrom at least one element from the group of elements consisting of iron,manganese, nickel, chromium, cobalt, copper, platinum, magnesium andantimony in order to create inter-metallic phases, e.g. aluminides, inthe boundary regions of the matrix, in which case another element from asecond group of elements consisting of manganese, antimony, chromium,tungsten, niobium, vanadium, cobalt, silver, molybdenum and zirconiumshould be added as a substitute for a part of at least one hardsubstance from the first group of elements in order to increase almostspherical or cuboid aluminides. This reduces the nicking effect of thesehard particles, so that the aluminium alloy can contain a higherproportion of soft phases, which also specifically improves resistanceto galling.

[0008] The properties which can be achieved from bearing metals alwaysrepresent compromise solutions. On the one hand it is desirable toimprove the resistance of such bearing metals or bearing metal alloys togalling by increasing soft materials such as tin or lead, as describedabove, but this can only be achieved at the cost of resistance tomechanical stress. In order to improve resistance to mechanical stress,it has been suggested in the prior art that silicon, amongst othermaterials, be added to the alloy. An alloy of this type is known frompatent specification DE 197 30 549 A1. This DE-A1 patent describes analuminium alloy containing 10% by weight to 25% by weight of tin as wellas added copper, nickel and manganese, which can be added to the alloyrespectively in a quantity of from 0.2% by weight to 2.0% by weight.This aluminium alloy also contains silicon in a quantity of from 0.2% byweight to 2.0% by weight and it is specified that the ratio of theproportion of copper as a percentage by weight to the proportion ofnickel as a percentage by weight and the proportion of manganese as apercentage by weight to the proportion of silicon as a percentage byweight should be between 0.6 and 1.5. The silicon increases hardness andreduces susceptibility to corrosive wear, preventing the formation ofcoarse aluminium-copper-manganese phases, instead of which preferrednickel-copper-aluminides and manganese-silicon aluminides are formed.After a heat treatment at 250° C., these aluminides are also finelydistributed.

[0009] An aluminium-tin alloy containing 7% to 20% of tin is known frompatent specification DE 43 32 433 A1. The bearing alloy additionallycontains up to 4% silicon along with other alloying elements, such asmanganese, magnesium, vanadium, nickel, chromium, zirconium, copper,antimony or titanium, for example. The mechanism whereby silicon causesthe matrix to harden is said to be due to the fact that it crystallisesout of the aluminium matrix in the form of silicon particles, whichthereby increases the strength of the bearing alloy overall. Since thesilicon particles are distributed throughout the structure, only thesoft aluminium matrix at the surface becomes worn, so that the surfacebecomes microscopically uneven. As a result, the silicon particles leftbehind as convex particles are capable of withstanding a high load,whilst simultaneously preserving the property of not bonding. Theconcave parts hold the oil so that the bearing alloys are able towithstand high load provided they have a thin film of oil and are inmetal-to-metal contact. The finely distributed silicon particles fulfilanother finction in that they wear down minute irregularities and burrson the co-operating shaft, thereby improving resistance to corrosivewear.

[0010] Tests have been already been conducted with transition metals,such as scandium for example, to determine whether they will produce aharder matrix when added to aluminium alloys. This was proposed in thecase of cast alloys in patent specification WO 96/10099 A, where thescandium content may be between 0.01% by weight and 10% by weight.

[0011] Scandium has also been suggested as a means of producing a hardermatrix in the case of wrought alloys (see e.g. WO 96/10099 A), which aredifferent, and patent specification WO 00/06787 A makes this suggestionfor a bearing metal alloy, whilst patent specification WO 00/06788 Atakes this same approach in the case of a binding layer. An alloydescribed in both of the above-mentioned documents may contain, forexample, 0.15% by weight to 1.0% by weight of scandium, a total of 3% byweight of one of the elements selected from manganese, copper orzirconium, a total of 4% by weight of one of the elements selected fromchromium, iron and cobalt as well as tin in a quantity of up to 6.5% byweight. The hardening effect is based on the fact that scandium formsso-called A₃M phases with aluminium and the finely disperseddistribution of these A₃M phases imparts a high ductility to thesealloys, which nevertheless exhibit no marked hardening behaviour. Inspite of the fact that solidification is reduced due to the productionprocess by heat treatments, these alloys have high values of mechanicalstrength. Patent specification DE 36 40 698 A1 discloses a bearing alloywith an aluminium base, which contains at least one element for thepurpose of forming soft phases, selected from the group consisting oflead, tin, indium, antimony or bismuth, as well as silicon as a hardelement and other reinforcing elements selected from the groupconsisting of copper, chromium, magnesium, manganese, nickel, zinc andiron, as well as refining elements from the group consisting oftitanium, boron, zirconium, vanadium, gallium, scandium, yttrium andelements selected from the rare earths with atomic numbers 57 to 71.

[0012] Patent specification DE 43 19 867 A discloses a multi-layer plainbearing, which, in addition to a protective shell of steel and anoverlay containing polytetrafluoroethylene, contains 5% by volume to 30%by volume of a metal filler and 5% by volume to 40% by volume ofpolyvinylidene fluoride, and has a bearing layer of bronze, such as atin bronze or tin-lead bronze, disposed in between.

[0013] A comparable multi-layer bearing is known from patentspecification EP 0 005 560 A, onto the metal support layer of which aporous base layer is sintered, containing 5% by weight to 25% by weightof lead, 5% by weight to 15% by weight of tin, the rest being copper,with polytetrafluoroethylene in turn deposited in the pores of the baselayer.

SUMMARY OF THE INVENTION

[0014] The objective of the invention is to propose a multi-layer plainbearing of simplified structure and at least the same durable,tribological properties as conventional multi-layer plain bearings.

[0015] This objective is achieved by the invention, in each caseindependently, by means of an aluminium alloy of the type outlinedabove, in which the element(s) of the first group of elements is (are)used in a total quantity of 4.5% by weight maximum, the element (s) ofthe second group of elements is (are) used in a total quantity of 8.5%by weight maximum, preferably 3.5% by weight, scandium and zirconium arepresent in a total quantity of 0.8% by weight maximum and the rest isaluminium and the usual impurities formed during melting, and by a baselayer made therefrom and a bearing element incorporating a base layermade from an aluminium alloy proposed by the invention. The resultantadvantage is that the composition of the aluminium alloy proposed by theinvention is such that the overlay can be applied directly onto the baselayer, which is disposed on the protective shell, which is made fromsteel for example, which means that the conventionally used bindinglayer and the nickel barrier can be dispensed with. The composition alsoobviates the need for the lead bronzes used as standard inhigh-performance bearings, enabling the use of materials and metalswhich are as far as possible harmless in terms of their toxicity andsuitability for recycling. In particular, the use of lead alloys can bedispensed with. The strength and in particular the dynamic strength ofthe resultant bond can be produced to higher values than is currentlypossible with standard three-layer bearings and using conventionalsteel/AlZn4,5 bonding. The tribological properties are also comparablewith those of AlSn6CuNi. A further advantage is the high resistance tocorrosion in contact with heavy oil and during use in gas-poweredengines as well as resistance to cavitation as compared with AlZn4,5.The bond with steel can be produced without the need for anadhesion-imparting intermediate layer. The base layer may also be usedfor sputter bearings. Yet another advantage is the fact that the cost ofmanufacturing these types of bearing elements is comparable with that ofexisting standard multi-layer bearings of the same quality. Thealuminium alloy proposed by the invention has the requisite resistanceto galling due to its capacity for plastic deformation, enabling it toadapt to geometric faults and variations, i.e. even if faults occur inthe overlay due to stress, the bearing element will still continue to beserviceable. An appropriate matrix toughness is obtained by means of theA₃M phases of scandium and zirconium with aluminium known from the priorart.

[0016] These properties are further improved due to the fact that theproportion of soft phase in the aluminium alloy is at least 0.1% byweight and the proportion of the element(s) from the second group ofelements represent(s) at least a total of 0.1% by weight, and theproportion of scandium and zirconium totals at least 0.05% by weight, inparticular 0.1% by weight, whilst the proportion of zirconium is in therange of between 0.01% by weight and 0.5% by weight, in particular inthe range of between 0.05% by weight and 0.23% by weight, and theproportion of scandium is between 0.05% by weight and 0.5% by weight, inparticular in the range of from 0.05% by weight to 0.25% by weight.

[0017] In one advantageous embodiment of the bearing element, the baselayer is disposed directly on the protective shell, which simplifies thestructure accordingly.

[0018] It is also possible to use an alloy with a base of lead, tin,bismuth, indium or copper for the overlay or the overlay may be a layerof plastic, in particular selected from a group consisting of polyamide6, polyamide 66, POM, silicone, PEK, PI, TPI, PEEK, PPS, PVDF, PTFE, aswell as mixtures thereof, enabling the aluminium alloy proposed by theinvention and the bearing element containing it to be adapted to a wholerange of different applications.

[0019] It is of particular advantage if the layer of plastic contains asolid lubricant, such as MoS₂, graphite or similar for example, in whichcase the bearing properties of this plastic layer will be furtherenhanced, enabling the bearing element to be used without any or withonly the smallest quantities of lubricant, such as a lubricating oil orlubricating grease, for example.

[0020] Finally, the overlay may also be provided in the form of alubricating varnish.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to provide a clearer understanding, the invention willbe described in more detail below with reference to examples illustratedin the appended drawings. Of the simplified schematic diagrams:

[0022]FIG. 1 illustrates a bearing element in the form of a plainbearing half-shell;

[0023]FIG. 2 is a table setting out various aluminium alloys proposed bythe invention;

[0024]FIG. 3 plots a comparison of tension-elongation values for variousaluminium alloys.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] Firstly, it should be pointed out that the same parts describedin the different embodiments are denoted by the same reference numbersand the same component names and the disclosures made throughout thedescription can be transposed in terms of meaning to same parts bearingthe same reference numbers or same component names. Furthermore, thepositions chosen for the purposes of the description, such as top,bottom, side, etc,. relate to the drawing specifically being describedand can be transposed in terms of meaning to a new position when anotherposition is being described. Individual features or combinations offeatures from the different embodiments illustrated and described may beconstrued as independent inventive solutions or solutions proposed bythe invention in their own right.

[0026]FIG. 1 illustrates a bearing element 1 proposed by the inventionin the form of a plain bearing half-shell.

[0027] It should be pointed out at this stage, that the invention is notrestricted to bearing elements 1 in the form of plain bearinghalf-shells and may also be used for other bearing elements 1 of thetype made from aluminium alloy, such as thrust rings, for example.Moreover, bearing elements can be produced not only as half-shells butalso as full shells.

[0028] The bearing element 1 illustrated in FIG. 1 is made up of aprotective shell 2, a base layer 3 proposed by the invention and arunning layer 4. The protective shell 2 is usually made from steel, butmay naturally also be made from other similar materials which fulfil thesame or a similar function, that is to say will provide the mechanicalstrength required of the bearing element 1. The mechanical strength ofthe bearing element 1 as a whole will depend on the respectiveapplication for which it will be used, and, this being the case, a wholevariety of copper alloys may be used, such as brass, bronzes, forexample. The protective shell 2 also imparts a certain degree ofdimensional stability.

[0029] The base layer 3 is made from the aluminium alloy proposed by theinvention. It consists of an aluminium matrix incorporating at least onesoft phase as well as hard particles. The at least one soft phase is atleast one element selected from a group of elements consisting of tin,antimony, indium and bismuth. The hard particles are at least oneelement selected from a second group of elements consisting of copper,manganese, cobalt, chromium and iron or the elements scandium and/orzirconium. These hard particles might also be provided in the form ofinter-metallic phases comprising the latter elements or the elementsfrom the second group of elements with aluminium or inter-metallicphases comprising said elements.

[0030] The soft phases on the one hand impart to the base layer 3 thecapacity to form a strong enough bond with the running layer 4 disposedon top and on the other hand impart the requisite galling resistance tothe bearing element 1 if faults occur in the running layer 4 whilst thebearing element 1 is in operation, thereby enabling the base layer 3 tocome into almost direct contact with a component to be supported, suchas a shaft, for example. The bearing element 1 is also rendered capableof embedding any hard particles which emerge due to wear when thebearing element 1 is in service. The hard particles impart the requisitemechanical strength to the aluminium alloy.

[0031] Suitable alloys for the running layer 4 are those with a base oftin, bismuth, indium or aluminium and optionally with a lead base or analloy with a base of CuPb and a high lead content. Tin alloys with ahigh content of tin offer particular advantages.

[0032] Bearing metals with a lead base which might be used include, forexample, PbSb10Sn6, PbSb15Sn10, PbSb15SnAs, PbSb14Sn9CuAs, PbSn10Cu2,PbSn18Cu2, PbSn10TiO2, PbSn9Cd, PbSn10.

[0033] Bearing metals with a tin base include SnSb8Cu4 and SnSb12Cu6Pb,for example.

[0034] The running layer 4, on the other hand, may also be made from acoating of plastic. Particularly advantageous examples are polyamide 6,polyamide 66, polyoxymethylene (POM), various silicones, polyaryl etherketone (PEK), polyimide (PI), TPI, polyaryl ether ether ketone (PEEK),polyphenylene sulphide (PPS), polyvinylidene difluoride (PVDF),polytetrafluoroethylene (PTFE) and various mixtures thereof.

[0035] If the sliding capacity of the plastic alone is not good enough,it is of advantage to add solid lubricants, such as molybdenumdisulphide (MoS₂), graphite or similar, to the various plastics.Quantities of various silicones may also be added.

[0036] Other additives may also be used in order to increase themechanical strength of the plastic layer, such as fibre matrices, suchas aramide fibres, for example, or hard substances such as carbides,oxides, nitrides, for example.

[0037] The plastic layer may also be provided in the form of a so-calledlubricating varnish.

[0038] Said plastics enable running layers 4 with good sliding andanti-galling properties to be obtained, which may also be used dry. Theyare distinctive due to their low maintenance requirements. It ispossible to operate with only a small quantity of lubricant or nolubricant at all. Water may optionally be used for lubricating purposes,which is of particular advantage if the bearing element 1 proposed bythe invention is used for pumps, for example. Apart from offering acorresponding weight reduction, susceptibility to nicking has also beenfound to be low.

[0039] In addition to the application described here, the bearingelement 1 proposed by the invention may also be used for a whole rangeof other applications and in particular can be used as a plain bearingor as a thrust ring in the automotive industry.

[0040] For the purposes of the invention, the aluminium alloy proposedby the invention contains the element(s) from the first element group ina quantity totalling a maximum of 4.5% by weight, the element(s) fromthe second group of elements in a maximum quantity of 3.5% by weight,scandium and zirconium in a total quantity of. 0.8% by weight maximum,the rest being aluminium and the usual impurities resulting from themelt. It is of advantage if the proportion of soft phase, in other wordsthe elements from the first group of elements, represent at least 0.1%by weight. Similarly, it has been found to be of advantage if theproportion of the element(s) from the second group of elementsrepresent(s) a total of at least 0.1% by weight. It is also of advantageif the proportion of scandium and zirconium also represents a total ofat least 0.1% by weight. The proportion of zirconium may be in the rangeof between 0.05% by weight and 0.5% by weight, in particular in therange of between 0.05% by weight and 0.23% by weight, and the proportionof scandium may be between 0.05% by weight and 0.5% by weight, inparticular in the range of between 0.05% by weight and 0.25% by weight.

[0041] Said figures given for the specified ranges should be understoodas meaning lower and upper limits of the respective ranges, which alsoincludes the respective peripheral ranges of 0.23% by weight to 0.5% byweight for zirconium and 0.25% by weight to 0.5% by weight for scandium.

[0042] Copper is absorbed in the aluminium as a solid solution,resulting in aluminium-rich mixed crystals, producing hardenablecomposite alloys, which are deformable and readily lend themselves torolling. Copper also has the effect of strengthening the matrix due tothe hardening of the mixed crystals, whereby Al₂Cu and Al₃Zr are formedindependently of one another, preferably from aluminium and zirconium,so that the resultant nucleus formation is not heterogeneous. Thesecrystallites start to separate more or less at the same time. Usingcopper increases the resistance of the aluminium alloy to fatigue andalso improves the resistance of the aluminium alloy to corrosion due tothe corrosive effect of oil-containing substances.

[0043] In order to improve the hardness properties, it is of advantageto add iron to the aluminium alloy. As explained above, like scandium,zirconium also forms so-called Al₃M phases with aluminium, enablingsolidification by means of inter-metallic hard phases. The addition ofsilicon can be dispensed with as a result, the advantage of which isthat the nicking effect caused by higher contents of silicon can be atleast alleviated or reduced. These two elements also help to produce afiner grain due to the formation of tri-aluminides.

[0044] The addition of manganese helps hardening and improves resistanceto corrosion. This also enables the recrystallisation temperature to beraised. It also prevents the formation of long-spiked, brittle Al₃Feneedles, especially if the iron content is low, because iron is absorbedby the AlMn crystals which are formed by preference.

[0045] Adding cobalt and chromium can also help to harden the aluminiumalloy.

[0046] The effects of the individual elements are known in principlefrom the prior art, for example from the documents mentioned above.Using these elements for an aluminium alloy, in particular for analuminium wrought alloy in said range of quantities, especially for abase layer 3 disposed between the protective shell 2 and the runninglayer 4 and combining said properties, e.g. anti-galling properties,adhesion, anti-corrosion properties, advantageously offers thepossibility of dispensing with various other layers which are providedas standard on existing multi-layer bearings, such as barriers toprevent migration, and these effects have not been described until now.

[0047] In other embodiments of the aluminium alloy, compositions weremade up as set out in table of FIG. 2 and their properties measured.

[0048] It should be pointed out that the alloy compositions listed inthe table should not be construed as limiting the scope of the inventionas they are merely given as selected examples and the person skilled inthe art will be in a position, from the teaching disclosed here, to makeup other compounds within the specified limits and these compounds arenot excluded from the protective scope of the patent.

[0049] In the examples listed, it was found that the mechanicalproperties of the aluminium alloy remain essentially constant within aspecific bandwidth. By bandwidth is meant that it is possible the adaptthe properties to suit a specific purpose, for example by adding one ormore elements in a greater or smaller proportion. By adding a largerproportion of copper as specified in example 9, for example, highertoughness can be obtained due to mixed crystal hardening.

[0050] The toughness behaviour and the properties of the aluminium alloygenerally speaking can be optimised to suit the situation in terms ofcost by varying the scandium or zirconium contents.

[0051] It is also possible to optimise the properties of the aluminiumalloy with regard to the addition of the elements forming the softphase, because mixtures adapted to the specific field of application canbe produced, depending on the ductility of the element, which also havea higher mechanical strength to a certain degree, in addition to thedesired anti-galling properties, albeit not to the same extent asachieved by the hard particles.

[0052] An aluminium alloy was also produced on the basis of acomposition comprisingAlSn1,3Sc0,2Zr0,26Fe0,1 and its tension-elongationbehaviour measured and plotted in comparison with AlSn25CuMn andAlZn4SiPb. The result is set out in FIG. 3, in which the elongation ε isplotted on the X axis and the nominal tensile stress σ_(z)[N/mm²] on theY axis. The measurements were conducted on strips prepared in accordancewith UN EN1002-1 using tension samples E 3×8×30 mm as specified in DIN50 120.

[0053] As is clearly evident from FIG. 3, the aluminium alloy proposedby the invention (uppermost curve) had an elongation of 0.1% comparedwith AlZn4SiPb (lowermost curve) and exhibited significantly highervalues than AlSn25CuMn (middle curve) with effect from an elongation of0.05%. In other words, in order to obtain the same elongation, the alloyproposed by the invention must be exposed to significantly higher forcesor tensions, i.e. the aluminium alloy has a correspondingly higherstrength than the aluminium alloys with which it was compared.

[0054] At a value of 241 N/mm² compared with a value of 181 N/mm² forAlZn4SiPb, the ultimate breaking strength of the alloy proposed by theinvention was also found to be significantly higher, as was the limit ofelasticity at 191 N/mm² compared with 85 N/mm² for AlZn4SiPb.

[0055] The corresponding values for AlSn25CuMn are 174 N/mm² forultimate breaking strength and 59 N/mm² for the limit of elasticity.

[0056] In short, it can therefore be said that mechanical properties canbe improved by using the aluminium alloy proposed by the inventionwhilst preserving at least comparable anti-galling properties, such asrequired of bearing elements 1, particularly for plain bearings.

[0057] The aluminium alloy and the bearing elements 1 made from it canbe produced using methods known from the prior art. Pure elements orhighly pure elements are used as the starting materials. The aluminiumalloy can be applied to the protective shell by rolling, plating, e.g.electro-plating, for example. The running layer 4 can be disposed onthis binding by said methods or alternatively by galvanic processes byspraying, etc..

[0058] Apart from rolling, the plastic layer may also be applied byspraying, dipping or by offset printing. Galvanic processes could alsobe used.

[0059] Although not absolutely necessary for the bearing elements 1proposed by the invention, various auxiliary intermediate layers maynaturally also be provided between the individual functional layers,depending on requirements, such as diffusion barriers, pure aluminiumlayers, a nickel insulation. etc..

[0060] For the sake of good order, it should finally be pointed outthat, in order to provide a clearer understanding of the structure ofthe bearing element 1, it and its constituent parts are illustrated to acertain extent out of proportion and/or on an enlarged scale and/or on areduced scale.

[0061] The individual objectives achieved by the invention may be foundin the descriptions.

What is claimed is:
 1. Aluminium wrought alloy with an aluminium matrix,incorporating at least a soft phase and hard particles, in which thesoft phase is at least one element from a first group of elementsconsisting of tin, antimony, indium and bismuth and the hard particlesare scandium and/or zirconium, and at least one element from a secondgroup of elements consisting of copper, manganese, cobalt, chromium,zinc, magnesium, silicon and iron, and inter-metallic phases ofscandium, zirconium with aluminium or aluminium with the elements fromthe second group of elements, characterised in that the element (s) ofthe first group of elements is (are) present in a quantity of a total of4.5% by weight maximum, the element(s) of the second group of elementsis (are) present in a quantity of a total of 8.5% by weight maximum,preferably 3.5% by weight, scandium and/or zirconium is (are) present ina quantity of a total of 0.8% by weight maximum, and the rest isaluminium with the usual impurities contained in the melt.
 2. Aluminiumalloy as claimed in claim 1, characterised in that the proportion of thesoft phase is at least 0.1% by weight.
 3. Aluminium alloy as claimed inclaim 1, characterised in that the proportion of the element(s) of thesecond group of elements represent(s) at least a total of 0.1% byweight.
 4. Aluminium alloy as claimed in claim 1, characterised in thatthe proportion of scandium and/or zirconium is at least a total of 0.05%by weight, in particular 0.1% by weight.
 5. Aluminium alloy as claimedin claim 1, characterised in that the proportion of zirconium is in therange of between 0.01% by weight and 0.5% by weight, in particular inthe range of between 0.05% by weight and 0.23% by weight.
 6. Aluminiumalloy as claimed in claim 1, characterised in that the proportion ofscandium is between 0.05% by weight and 0.5% by weight, in particular inthe range of between 0.05 and 0.25% by weight.
 7. Base layer made froman aluminium alloy for a bearing element, which may be disposed betweena protective shell and a running layer of the bearing element,characterised in that the aluminium alloy is as claimed in one of claims1 to
 6. 8. Bearing element, in particular a plain bearing or thrustring, with a protective shell, a running layer and a base layer disposedin between, characterised in that the base layer is made from analuminium alloy as claimed in one of claims 1 to
 6. 9. Bearing elementas claimed in claim 8, characterised in that the base layer is disposeddirectly on the protective shell.
 10. Bearing element as claimed inclaim 8, characterised in that the running layer is made from an alloywith a base of lead, tin, bismuth, indium or copper.
 11. Bearing elementas claimed in claim 8, characterised in that the running layer is alayer of plastic.
 12. Bearing element as claimed in claim 11,characterised in that the plastic layer is selected from a groupconsisting of polyamide 6, polyarnide 66, POM, silicones, PEK, PI, TPI,P SEK, PPS, PVDF, as well as mixtures thereof.
 13. Bearing element asclaimed in claim 11, characterised in that the plastic layer contains asolid lubricant, such as MoS₂, graphite, for example.
 14. Bearingelement as claimed in claim 8, characterised in that the running layeris a lubricating varnish.